To improve the probability of earlier breast cancer detection while reducing the number of unnecessary needle biopsies, Physical Optics Corporation proposes to develop a new Fast Acousto-Optic Tomography System (FAOTS) as an auxiliary tool for the conventional ultrasound breast examination that often follows a screening mammography. The innovative FAOTS will provide images with better contrast than sonography, because the optical properties of normal tissue and tissue with neoplasia differ much more than their acoustic properties. FAOTS will use a tightly focused ultrasound beam to shift the frequency of photons at a certain location in a tissue and detect them using a heterodyne technique utilizing a parallel signal acquisition by multiple photodetectors on a fast CMOS chip. The utilization of a high-speed (>4000 fps) CMOS camera with a large memory capacity enables signal detection in a short time interval, so speckle decorrelation in the live tissue will not affect system operation. In Phase I, POC experimentally demonstrated the capability of the laboratory prototype of obtaining high contrast signals with a speed exceeding the speckle decorrelation time. In Phase II, POC will design and fabricate an engineering FAOTS prototype and conduct a demonstration of its capability of mapping the optical properties of patient breast tissue at Harbor-UCLA Medical Center in Torrance, California. The fully developed FAOTS will provide a spatial resolution of ~0.4 mm, which is significantly better than Optical Diffuse Tomography (ODT). The FAOTS technology will enable positive predictive value (PPV) improvement in breast cancer diagnostics, with earlier detection of smaller tumors, thus enhancing patients'chances for long-time survival after cancer treatment. The successful demonstration of the FAOTS technology for mapping the optical properties of breast tissue will broaden the perspective for the extension of the FAOTS technology using multiple light wavelengths for improving image contrast. It will also facilitate development of special instrumentation for mapping the optical properties of other internal organs, and better diagnostics of tumors in these organs (e.g., prostate).